Valid Arguments and Logical Fallacies
"The venerable tradition of respectful argumentation, based on evidence, conducted with courtesy, and
leading to the exposition of truth, is a precious part of our heritage in this land of freedom. It is the duty of
educated men to understand, appreciate and perpetuate this tradition."
------ James P. Shannon
A VALID ARGUMENT is a statement that exhibits a logical pattern of reasoning. This MEANS that a valid
argument must have relevant, verifiable proof supporting a conclusion.
When making an argument, the writer must make a point and support that point.
As readers, we must recognize the point and determine whether or not that point is supported by relevant
and verifiable proof. To evaluate an argument, the reader needs to ask these two questions:
1. Is this argument logical?
2. Are these reasons (given to support the conclusion) true?
Recognizing valid arguments is a difficult task that can be hindered by a reader's lack of background on
issues and topics. In fact, it is easier to recognize an argument that is INVALID than one that is VALID.
The recognition of INVALID ARGUMENTS can be facilitated by the reader's familiarity with twelve common
fallacies that are used by writers.
These fallacies may be used by writers who are so intent on making a point or gathering support for a
conclusion that they inadvertently fail to use logical reasoning to prove their point. Fallacies may be used
intentionally, either to mislead, to divert attention from the real issues, or as an aid to sell a product.
TWELVE COMMON LOGICAL FALLACIES
1. F
AULTY CAUSE AND EFFECT
(post hoc, ergo propter hoc). This fallacy falsely assumes that one event
causes another. Often a reader will mistake a time connection for a cause-effect connection.
EXAMPLES: Every time I wash my car, it rains.
Our garage sale made lots of money before Joan showed up. Obviously,
she scared off all the customers.
2. N
ON SEQUITUR
. The conclusion is not necessarily a logical result of the facts.
EXAMPLES: Mrs. Sedik really knows math; she would be an excellent math instructor.
(The conclusion may not be valid. Here an INFERENCE is substituted for a
logical conclusion. One cannot automatically conclude that all individuals
who are good at math can teach this subject well.)
